How bad is it to use Auto ISO?

Wilt wrote in post #17688704
With M mode, you inherently can do what the EC does (for automation modes Av and Tv) simply by not aligning the 'needle' to be centered on the scale in the viewfinder!!!

As for 'too dynamic a situation'... if the sun is out and there are no clouds in the sky, or if the sun it always behind overcast sky, the LIGHT IS NOT CHANGING. You meter indicates when a white jersey or a black jersey runs in/out of the frame, but the LIGHT IS NOT CHANGING, so there is absolutely ZERO need to alter exposure. Just because a black jersey reflects less light to the in-camera meter, and a white jersey reflects more light to the in-camera meter, does NOT mean that light falling upon the scene (and the necessary exposure setting) is changing, too.

Mr. Ipsum could easily have used M mode for his whale watching shooting...it the clouds were unbroken overhead, the light falling upon the scene was not changing...only the amount of sky vs. water was changing (affecting the reflected light), but not the amount of illumination (not affecting the incident light).

If the sun is playing hide and seek constantly due to broken cloud cover, THEN the light IS changing, and an automated mode (Av or Tv or Auto ISO) can be handy for keeping up with the perpetual changes in light which falls onto the scene.

I understand the ETTR concept in manual mode. If all anyone did was chase the needle, auto iso would be all we'd need, whereas manual mode allows us to shift as we please. You make an interesting point about light consistency. I'm not sure if I'd need the same iso at 70 as I do at 200, but it makes me wonder. Worth some experimentation on my end.

I use auto ISO frequently. It’s very useful when you’re shooting fast moving events where you don’t have time to constantly adjust the exposure, and the lighting is constantly changing. Each second you spend messing with your camera is an opportunity to miss a key moment you won’t get a chance to shoot later.

The better the low-light performance of these cameras get, the less I care about what ISO is being used. This is why I own FF cameras. Auto ISO works best when there’s a good implementation of a minimum shutter speed and max ISO, that way you know that without constantly monitoring the exposure, you aren’t pushing past certain boundaries that will ruin your shot.

That said, if I’m shooting a landscape, I’m more cognizant about the DR implications involved with pushing the ISO, so it’s full manual there. So its horse for courses like anything else in photography, but in instances where auto iso is needed, its an extremely valuable feature IMO.

mystik610 wrote in post #17691063
I use auto ISO frequently. It’s very useful when you’re shooting fast moving events where you don’t have time to constantly adjust the exposure, and the lighting is constantly changing. Each second you spend messing with your camera is an opportunity to miss a key moment you won’t get a chance to shoot later.

The better the low-light performance of these cameras get, the less I care about what ISO is being used. This is why I own FF cameras. Auto ISO works best when there’s a good implementation of a minimum shutter speed and max ISO, that way you know that without constantly monitoring the exposure, you aren’t pushing past certain boundaries that will ruin your shot.

Of course, if the lens is not allowed to open more or the shutter speed get slower, when light gets too low, a maximum ISO really doesn't do what it claims to do, as an ISO 6400 shot under-exposed by 3 stops is still an ISO 51200 shot, even though the file's EXIF says 6400. If you're shooting JPEG, you have posterized and tiled the shadows. Limiting the max ISO can be very useful to trade off stopped-down lens sharpness or freezing shutter speeds for less noise, but only up to a point, and then when there is no Av or Tv parameter that can accommodate less light, the real ISO exposure index keeps rising beyond that point. It would be nice if we could define full tables of ISOs, Tv, and Av values for the range of ambient EV values as user-defined program modes.

One situation in which a max ISO has a clear use with no drawbacks is when you use fill flash and would prefer for the flash to take over when ambient light gets too low. That way, your ambient light may fall off when the exposure index is much higher than the limited ISO setting, but the flash fill creates enough light to keep the ISO exposure index from rising. For example, if you set the max ISO to 3200, and set the ambient EC to -1, and the flash EC to -1, then the total light should give an ISO exposure index of 3200 (half of it from ambient, and half from flash) when the camera meters for ISO 3200. When ambient light drops further, the flash fill is still there, so you always have an ISO 6400 exposure index, at a max, as long as the flash has enough power to deliver it (which depends on distance and f-number). So, distance is the only thing that can keep you from an ISO 6400 exposure index; not a lack of light.

It's a shame that almost 20 years into digital cameras that they all don't have an "expose to the right" exposure mode, where "EC" is actually a percentage of pixels allowed to blow out in the RAW or JPEG, whichever you are shooting. Even DLSRs have decent-res off-sensor meters now.

John Sheehy wrote in post #17691088
It's a shame that almost 20 years into digital cameras that they all don't have an "expose to the right" exposure mode, where "EC" is actually a percentage of pixels allowed to blow out in the RAW or JPEG, whichever you are shooting. Even DLSRs have decent-res off-sensor meters now.

It sounds like a nice feature at first glance, but the limitation of the ETTR concept applies whether the camera attempts to do ETTR or the user follows the ETTR principle blindly...in both cases, the most appropriate exposure is determined by which pixels in the shot capture areas in the scene which have no useful detail...where simply keeping those pixels on the histogram is a wasted principle to apply to them.

The non-thinking photographer or the exposure algorithm for ETTR today both mindlessly attempt to keep things on the histogram. In practice, the photographer should decide which portions of the scene HAVE important detail and which are merely 'go white' areas (the sun's reflection on a chrome bumper is one such example of no-detail-important).

The other limitation of the concept, unless manufacturers put in a field of data in the EXIF to remind the photographer during postprocessing just how much (or how little) the exposure is biased to the right (an 'auto EC' value in the EXIF?!) -- is that the ETTR shot does not portray things necessarily 'at their inherent brightness' and so the photographer does not know how much to compensate the shot back to the left during postprocessing to restore 'inherent subject brightness' to the shot. Otherwise we have 18% grey cards exposed to very light grey, and the shot is not portraying reality in the scene any longer.

It's a nice concept, but there are challenges to be resolved before the feature is truly useful. Kinda like Auto ISO has been a nice concept in cameras for almost 10 years, but only the very newest models introduced over the past year can DO what the photographer wants to do (EC during Auto ISO)!

I never used it until I got my 6D, now I use it pretty much all the time unless I want better control over the total exposure.

I usually use it in Av mode with the min shutter speed setting set depending on which lens I'm using. The benefit of using Av mode with min shutter speed is that you can still do exposure compensation, you can't do this in M mode, at least not on the 6D.

Or for more control (of the shutter speed but with the loss of exposure compensation) in M mode, I've never used it in Tv mode but I don't usually use Tv mode at all. Av is used when I just want to control DOF and M mode for anything else.

To me it is clear that it is a matter of "de gustibus non est disputandum"; translated "In matters of taste, there can be no disputes". Everyone's personal preferences are subjective opinions that aren't necessarily right or wrong. In fact they may change depending on the circumstances and the more important thing is to realize the when and why to change, not to get locked into any given set of camera settings. I do a lot of landscape work at infinity focus and I also come from an era (late 1950's) where everything was manual and you carried a light meter in your pants pocket. As I moved to 35mm film cameras that had so-called "automatic" capability I got used to using settings very similar to Tv, and that is what I use today for a lot of what I do. But I am ever watchful of what the camera selects for f/stop and the lens on the camera. Having said all that when I am taking images of my 18 month old grand niece, then I will likely revert to Av, still fixed ISO, with the aperture selected for depth of field.

If you understand the exposure triangle IMO ISO can be one of the least critical parameters. For much of my outdoor landscape work I use ISO 400 but again I am always aware of the ramifications of that setting and how it interacts with shutter speed and aperture. Should I decide to capture that bee on a flower, then I know I'll need to make some changes to improve the image.

I use Auto ISO with Av at events when lighting can change. I know myself and I can forget to change ISO settings moving from light to dark and vice versa.

Has anyone mentioned that on certain camera bodies, you can set the upper limit of Auto ISO? My Auto ISO is limited to 1600. If I want to shoot 3200 or above, I make that conscious decision manually.

John Sheehy wrote in post #17691088
Of course, if the lens is not allowed to open more or the shutter speed get slower, when light gets too low, a maximum ISO really doesn't do what it claims to do, as an ISO 6400 shot under-exposed by 3 stops is still an ISO 51200 shot, even though the file's EXIF says 6400. If you're shooting JPEG, you have posterized and tiled the shadows. Limiting the max ISO can be very useful to trade off stopped-down lens sharpness or freezing shutter speeds for less noise, but only up to a point, and then when there is no Av or Tv parameter that can accommodate less light, the real ISO exposure index keeps rising beyond that point. It would be nice if we could define full tables of ISOs, Tv, and Av values for the range of ambient EV values as user-defined program modes.

One key point regarding Auto ISO is that it’s not a ‘set it and forget it’ feature. Even if the ISO is being set automatically for you, the mental balancing act that is the exposure triangle still has to happen, and I constantly monitor what ISO and SS is being assigned to a shot, even if I’m not actively setting it myself. If I do start to hit the boundaries of what I’d consider acceptable for a shot, then some intervention is required, whether it means using a faster lens, manually pushing the ISO higher or setting the ISO lower, whether to allow my speedlights to expose the ambient (IF POSSIBLE) etc etc. Auto ISO saves you from having to set ISO, but never eliminates the need to think about the ISO setting